Heater



July 1, 1941. A E. w. RITTER 2,247,849

HEATER Filed April 1, 1938 3 Sheets-Sheet l July 1, 1941- E. w. RrrTER w 2,247,849

HEATER Filed April l, 1958 3 Sheets-Sheet 2 July l, 1941.

E. w. RITTER HEATER Filed April 1, 195s 3 Sheets-Sheet 3 Patented July l, 1941 UNITED sTA-Tss PATENT vorifice Emil W. Ritter, Chicago, Ill.

Application `April 1, 1938, Serial No. 199,368

8 Claims. (Cl.

This invention relates to heaters, furnaces, and the like and is more particularly concerned with domestic heaters especially constructed for the use of gas as a fuel, but it is to be understood that this invention is not necessarily limited to any particular kind of fuel.

The principal feature of the present invention is the employment of a plurality of separate and independent passages from the burner chamber to the outlet of the heater which are arranged to provide spaced-apart tortuous paths for the heated fluid, and in which the passages exterior thereof through which the fluid to be heated moves are also generally tortuous in character, thereby greatly improving the thermal contact between the fluidto be heated and the iiues or passages carrying the heated medium. It is ralso a feature of this invention to provide for a -great area or zone of thermal conductivity but in which an adequate volume of flow is accommodated at the desired rate.

It is also a feature of this invention to pro-v vide a heater in which the fluid to'be heated will be divided into relatively shallow streams, of gradually increasing cross section, passing over'relatively shallow fiues, of gradually decreasing cross section, which flues likewise divide the gases of combustion into relatively shallow streams. Thus, a greater portion of the fluid to be heated and/or a greater portion lof the heating medium can be brought into closer proximity to the heating surfaces of the heater than is possible where the fluids move through paths of relatively lar-ge cross section. By virtue of this arrangement, an increase of heat exchange andtherrnal efficiency are realized.

Another feature of this invention resides'in the provision of a plurality of separate and independent passages for the heated products of combustion, which passages are progressively decreased in cross section in substantially the same ratio that a unit quantity of the heating medium is decreased in volume as heat is eX- tracted therefrom. It is also a feature of this invention to provide for progressivelyy increasing the size of the passages carrying the medium to be heated, such increase Vin size being pro-Y portional to the expansion of such fluid as 'it absorbs heat from the heating medium.

A further feature of this invention, particularly in connection with the provision of a plurality of separ-ate independent passages for the productsof combustion, resides in the provision of damper means operative to adjust the prof' to feeintate a. gravity movement of' the fluid to be heated through the heater. It is also a feature of this invention to provide such'a multiple flue construction for use with heatersin which the iiow of the medium to be heated is in the natureof a forced circulation.

A further feature of this invention'includes the provision of a hot water or steam heatingl boiler having certain or all of the above-mentioned features and in which one or more downcirculation chamber is provided at one or both sides.

'It is a further 'feature of this invention to employ certain or all of the above-mentioned.

features in forms of heat exch-ange devices other,

f than heaters. For example, a cooling orv airconditioning unit may be provided with the fea-I tures of this invention which improve the thermal contact'between the warm and cool fluids. l Another feature of this invention is the provision of means associated with the stack chamber to take Acare of condensate and to conduct the same away from portions of the heater so as to prevent corrosion and deterioration of such parts.Y y

These and otherobjects and advantages of the present'invention will be apparent to those skilled in the art after a considerationl of 'the' following (detailed description, taken in conjunction with the .accompanying drawings.

" In the drawings:

`Figure 1 is a vertical longitudinal section tive, illustrating the rear end of the combustion chamber and the manner in which the heated combustion gases pass into the several fiues;

Figure 5 is a` longitudinal vertical section `V,taken through a modified form of heater;

Figure 6 is a section similar to Figure 2 but shows a further form in which both the combustion gases and the circulating air have separate and independent spaced-apart passages in intimate thermal contact with each other;

Figure 7 is a fragmentary detail of the iin construction connecting the return bends of the ues to the heater casing in a manner to accommodate dimensional changes in the ues due to expansion and contraction thereof; and

Figure 8 illustrates the use of down-circulation chambers at the sides of the heater, adapting the present invention for use in a hot water or steam heating boiler.

Referring now more particularly to Figures 1 to 4, the casing of the heater is indicated in its entirety by the reference numeral I and includes side sheets 2 and 3 and end sheets 4 and 5. Any or all of the end or side sheets may be made removable or have removable sections or doors. At their lower edgesv the sheets 2 to 5 are connected to a bottom sheet or plate 'I, and immediately above the latter the side sheets 2 and 3 are provided with air inlet openings Ill. The upper portion of the casing I includes a hood or bonnet I2 in which, in Figure 1, two outlets I3 and I4 areprovided from which the heated air is conducted to the space to be heated.

An intermediate wall 20 is disposed in the lower portion of the heater and extends from the front to a point adjacent the rear, where it connects with a vertical wall 2|, the upper portion of which extends rearwardly, as at 22, and is joined to a rear wall 23. The plate 20 forms the upper wall of a combustion chamber indicated in its entirety by the reference numeral 25 and which includesside walls 26 and 2l, and a bottom wall 28. The front end of the combustion chamber 25 is closed by a removable plate 30 or the like, which may have an opening to provide for lighting the burner, and at its rear end the chamber 25 communicates with the space at the rear of the heater between the plate 2l and the rear wall 23. This space, indicated at 3|, is gas tight and constitutes what might be termed a header, the bottom of which is formed by thev rearmost section 32 of the bottom plate 28 of lthecombustion chamber. The section 32 has side wings 33 and 34 Y arranged as best shown in Fig. 4. If desired, the sections 32, 33 and 34 may be made separate from the combustion chamber 25. Small triangular pieces 3'I and 38 are secured to the forward edges of the wall sections 33 and 34 and the adjacent portions of the plate 2| and the combustion chamber.

A stack for the heater is indicated at 4U and extends downwardly through the hood or bonnet I2 and into a stack chamber 4I formed by top and bottom sheets 4.2, side walls 43 and vertical walls 44. Access to the stack chamber is had through a clean-out door 46. The lowermost end portion ofthe stack 40 extends below the upper wall 42 and vis held in place therein by any suitable means, such as a collar 45. Al condensate trap 48 is disposed immediately underneath the stack 4|] and includes a shallow receptacle 49 and a drain pipe 50, both preferably formed of cast iron or other suitable corrosion-resistant material. Condensate and the like that drips from the stack 4|) will thus be received by the condensate trap 48 but will not come into contact with the walls of the outlet chamber 4I, so that the latter are thus protected from corrosion and the like from this source.

A burner 60 is disposed within the combustion chamber 25 and is provided with the usual outlet openings BI through which the combustible gas flows. The burner 60 is supplied with gas from any suitable source and controlled in any suitable manner. The burner 6K0 is an elongated part that extends substantially the entire length of the combustion chamber. The inlet for the combustion supporting air is at the front 30 of the combustion chamber, and in order to prevent starving the inner gas flames and supplying excessf air to the outer gas flames, means oonstructed according to the principles of the present invention have been provided for insuring a uniform supply of combustion supporting air to the burner throughout its length.

Referring now more particularly to Figures 1 and 3, three independent conduits 63, 64 and 65 have been provided in overlapping relation and With closed inner ends but with open outer ends. These conduits have openings 5l, 68 and B9 (Fig. 3) which are disposed directly underneath different portions of the burner 60 and serve, respectively, as separate conduits directing quantities of fresh air to different portions of the burner 60. It will be clear from Figure 1 that the openings 6l of the conduit 63 are spaced inwardly beyond the closed end of the conduit 64, and the openings 68 of the latter are spaced inwardly of the closed end of the shorter conduit 65. Each conduit is supplied with a damper as at "I0, 1| and l2, in the form of a flat plate having openings which, in the full open position, are adapted to register with the openings of the air inlet conduits. Each plate or damper is provided with a handle as at 13, 'I4 and '|5, whereby each damper maybe adjusted to provide the exact amount of air necessary to secure the. desired combustion. `In order to illustrate the operation of the dampers, Figures 1 and 3 show the damper 'I2 in a slightly closed position while the damper 'II is shown in a fully closed position and the damper Ill is shown in a fullyopen position. It will be understood that, in practice, these dampers will be adjusted to secure the proper combustion of the particular fuel in use, and then it is rarely necessary to change the adjustment, unless, of course, the'characteristics of the fuel are varied. Usually, the several dainpers are each in about the same position.

The hot gases of combustion pass from the burner chamber 25 into the header chamber 3| at the rear end of the heater. A plurality of separate and independent flues lead from the header chamber 3| to the stack chamber 4I, andthe flue construction will now be described.

As many iiues may be provided as desired or necessary, but for purposes of illustration I have shown in Fig. 1 three separate and independent ues 8|, 82 and 83 extending from the combustion chamber to the stack chamber. Each flue is in the form of a shallow, tortuous or zig-zag passage, and the corresponding sections of the ilues are spaced apart. The ilue 8| has an inlet 86 (Fig. 4) and a generally or substantially horizontal run S1, at the end of which is a return bend 88 of generally short radius. At this point the ilue 8| has another generally horizontal section 89 which extends backwardly over the section 8l but spaced apart, as indicated at Si), and is connected with another return bend 3| of generally large radius. The return bend 9| connects to another generally horizontal section 92 at the end of which a third return bend 93 directs the flue gases into a fourth generally horizontal run 94, the endof which extends into the stack chamber 4|, as'at 95. f

The other flues 82 and 83 are of similar construction. The ue 82 has an inlet |08, a generallyvhorizontal run |01 disposed-below the section 81 of the ue V8|, a return bend |08 disposed in spacedv relation about the return bend 88 of the flue 8|, another generally horizontal run or section |09,a' return bend disposed in spaced relationinwardly of the return bend 9|, a substantially horizontal section ||2, another return bend ||3, and a generally horizontal section 'I I4 the end of which opens into the stack chamber 4| latl I I5. The other flue 83 has an inlet |26, a `generally horizontal run |21, a return bend |28 of large radius, a 'generally horizontal section |29, a small return bend |3I, another generally horizontal section |32, a return bend |33 of large radius, anda nal section |34 disposed about the portions 94 and ||4 of the other iiues, the section |34 of the flueV 83 opening into the stack chamber 4|y at |35. It is to be understood that by describing the 4flues as generally or approximately horizontal I intend to embrace constructions that are inclined slightly as well as those that are truly horizontal.

The return bends 88, |08 and |28 are connected to each other and to the casing by ins |36. 1 Similarly, fins |31 connect the return bends 9|, and l|3| tothe casing I and fins |38 connect the return bends 93,-'I I3 Iand |33 to the casing. The ns |35, |31`1and |38 cooperate with the flues to prevent any short-circuiting of the air movements at theends of the casing and also aid in supporting the lues.l

While for purposes of clarity the fins |36, |31 and |38 are shown as single plates, in lactual practice, as illustrated in Figure 7 which shows the details of the'n construction |38, each of -1 the above Vmentioned fins consists of two strips disposed in overlapping relation so as to permit the ues to expand and contract under temperature changes, In Figure 7 the n'construction |36 includes a strip |38a that is fixed to the front sheet 5, as by spot welding -or the like, and a strip |3617 is'xed to the adjacent return bendl |28 in any-suitable'manner, which may also be by spot welding, the strips |36a and |361) over lapping oneanother. The other ns |36, |31 and' |38 are'of lsimilar construction, so that a further description is not necessary.

The nues are so constructed that Athe spacing between the edges of the lower sections 81, |01 and |21 and the adjacent portions of the sides of the casing I slightlyless than the corresponding spacing between the edges of the next upper bank 'of sections' 89, |09 and |29 `and the sides of rthe casing. Similarly, the spacing between the edgesof the ue sections 92, ||2 and I 32 and the sides of the casing is slightly greater than the corresponding spacingbetween the edges of the ue sections 89, |09 and |29 and the sides of the casing, and thespacing` between the edges of the uppermost flue sections 94, ||4 and |34 and the sides of the casing is greater than the corresponding spacing for the lower flue sections 92, I|2 and |32. Actually, the proportions of the ues and their position betweenthe sides of the casing are such that the spaces between the edges of the flues and the sides of the casing vary substantially proportionally to the volumetric increase in the air 'or other fluid that is heated by its passing upwardly through vthe, heater.

Generally, thevvariation of the spacing between the edges of theflues andthe sidesof the casing corresponds to the variation in the spacing vertically between the various fluev sections, -whereby the passagesrfor the upwardly moving mass of uid to be heated gradually increase in cross section Iat' substantially the same rate that the volume of the uid being heated increases.

The generally horizontal sections of the ues 8|, 82 and 83 are not disposed directly above one another but are staggered laterally of the fur'- nace in sets or banks of three flue sections each, as best shown in Figure 2. From this figure it will .be seen that the lowermost horizontal sections 81, |01 and |21 are disposed with the low`r ermost horizontal section |21 substantially in engagement with the side wall 2 and with the'next succeeding upper sections |01 and 81 displaced laterally to the right (Fig. 2), the section 81 being spaced from the'wallv 3 an appreciable distance. The next set of three horizontal sections 89, |09 andY |29, are offset or staggered from the wall 3 to the wall 2, and then the next three sections, I32, l2 Iand 92 are staggered from the rWall 2 to the wall 3. As a result of this construction, the air to be heated, which enters the openings |0 and rises yalongside the combustion ychamber 25, moves upwardly in the paths indicated by the arrows in Fig-ure 2. The offset or staggered relation of the horizontal sections |01 and 81 serves to divide the upwardmovement of the air into three laterally movable streams, thereby increasing the thermal contact between the air to be heated and the combustion gas passages. The divided air streams in their upward passage through the heater then join at the ,point A in Figure`2 and are again dividedvby the oiset horizontal flue sections |09, |29 and |32. These separate streams are then joined at point B and again are separated by the flue sections ||2, 92 and 94 into separate streams and again are joined at C. Fin-ally, the heated air `emerges from the upper horizontal sections 94, ||4 and`|34 and passes between a pair of baffles |40 and |4| which brings the several streams of upwardly moving air together before it enters the distribution bonnet or hood I2, whereby stratication is eliminated.

Three dampers |43, |44 and |45 are disposed at the inlet ends 8S, |06 and |25 of the flue sec-r tions 81, |01 and |21, and may be'a'djustedl by any suitable means, either manually or thermostatically. Generally, if the heater is to be operatedv at or near its full capacity, the flue d am-'Vv bustion gases `forced to travel through only one of the ues'. y

One of the features of thisv invention resides in the particular formation of the flues and air passages'. The combustion gases are, of course,

hottest when they leave the combustion chamber and cooled as they pass through the spaced independent iues, while the air to be heated has its-temperature increased, in that the air' entering the furnace through the openings I0 is cooler than when it enters the bonnet or hood I2. As willl be apparent from Figures 1 and 2, the cross sectional area of each of the Iiues 8|, l82v and 83 is greatest at the sections thatV receivev the hot combustion gases, and gradually dimin` ishe's until, at a point where the nues enter the stack chamber 4|, the `cross sectional area has been reduced approximately one half. Conversely, the passages between the flues which accommodate an upward and side-to-side or zig' zag movement of the air, are smallest in eiective cross section where the ues are the largest, the effective cross section of the air passages between the lues progressively increasing, as will be clear from Figure 2. Thus, a steady uniform movement of the combustion gases and the air to be heated occurs throughout the heater, since as the combustion gases lose their heat the effective size of the ues decrease in substantially the same proportion as the volume of the combustion gases decrease and, for the same reason, the effective cross section of the air passages progressively increases in proportion to the increase in volume due to the heat being absorbed from the combustion gases.

Referring to Figure 5, the heater shown in this figure is of somewhat simpler form in that the flues, instead of being separate and independent from the combustion chamber to the stack chamber, are formed in a plurality of serially connected banks, each bank being slightly inclined and composed of a plurality of lues connected at opposite ends to a common header chamber. In the construction shown in Figure 5, the casing is of generally rectangular configuration and includes a vburner chamber |5| of substantially the same construction described above. The outlet of the burner chamber, indicated at |52, leads into a header chamber |53 into which three slightly inclined'flues |54, |55 and |56 are connected. The other ends of the flues communicate with a return bend chamber |58 which receives all of the combustion gases from the three separate ues |54, and |56, and directs them into the next bank of ues |60, |6| and |62. The opposite ends of this latter bank of flues communicate with another return bend chamber |64 into which the third bank of flues |61, |68 and |69 extend. Another return bend chamber |13 leads the gases of combustion from the third bank of flues |61, |68 and |69 into a fourth bank of flues |16, |11 and |18, the latter discharging into a stack chamber |30 into which the stack |8| extends.

It will be noted that the ues making up each bank are disposed in parallel relation and slightly inclined from end to end, so that the combustion gases pass in a generally zig-zag formation from the combustion chamber to the stack chamber. The lower bank of nues, which have a cross section similar to that illustrated in Figure 2, are inclined upwardly an-d forwardly from the header chamber |53, and the next bank of lues are inclined in the other direction, and so on. The lowermost bank of lues are of larger cross section than the others, the cross section of the ues of each bank varying from bank to bank so as to correspond generally to the decrease in volume of the combustion gases as heat is extracted therefrom. The air to be heated passes in and out among the ilues, which are staggered or offset in the manner illustrated in Figure 2, in substantially the same Way as described above. The ends of the flues, as well as the various headers and return bend chambers, preferably are supported by two Vertical sheets |84 and |85. All parts of the flue passages and associated parts through which the combustion gases pass, including the inlet and outlet chambers ,|53 and |80, and all return bends or return bend charnbers, are formed of corrosion resistant material.

Figure 5 shows an arrangement in which the flues are inclined longitudinally, and if desired the flues may be inclined in a lateral direction. either with or without the feature of longitudinal inclination.

Referring now to Figure 6, the casing of the heater is indicated by the reference numeral 200 and includes a burner chamber 20| of substantially the same construction described above. The ilu-es above the burner chamber 20| are arranged in banks and may be either separate and independent from one end to the other, as indicated in Figure 1, or may be arranged with common return bend chambers, in the manner shown in Figure 5. Whatever the arrangement at the ends, the first bank of flues 205, 206 and 201 is constructed to receive the hot combustion gases, as from a header chamber, such as the chamber 3| shown in Figures 1 and 4, or the chamber |53 shown in Figure 5. The lowermostl ue 205 is inclined in one direction laterally, while the other nues 206 and 201 are inclined in the other direction, in addition to being staggered or oiset in a manner similar to that indicated in Figure 2. By virtue of this arrangement, the rising mass of air, as it is heated, is directed by the lateral pitch of the ilues in' the direction in which the air should flow. The next bank of ilues above the lues 205, 206 and 201 comprises the flues 2|0,

2| and 2| 2, which are connected, respectively, to the nues 205, 206 and 201 if arranged in the manner indicated in Figure 1, or to a return bend chamber such as indicated at |58 in Figure 5. From Figure 6 it Will be noted that the lowermost ilue 205 is disposed against the left hand side Wall 202 of the heater and that the lowermost lue 2|2 of the second bank is connected to or disposed against the opposite side Wall 203. A closure plate 2|5 is disposed in a vertical plane and connects the left edge of the ue 2|| to the left edge of the ue 201. A similar but larger closure plate 2| 6 connects the left edgeV of the flue 2|0 to the left edge of the flue 206. As indicated by the arrows, this particular construction divides the rising air into three separate and independent paths.

The third bank of flues is indicated at 22|,

222 and 223,'which flues are connected Vto receiveV the combustion gases vfrom the lower ues 2|0,

2|| and 2|2. A closure plate 225 connects the right hand edge of the liue 222 tothe right hand edge of the flue 2|0, and another closure plate 226 connects the right edge of the flue 223 to the right edge of the ue 2| thereby continuing the' separate and independent passages for the rising air. The uppermost bank of flues is indicated at 23|, 232-and 233, and a closure plate 235 connects the left edge of the flue 232 to the left edge of the flue 223, and another-closure plate, 236, connects the left edge of the uppermost ue 233 to the left edge of the flue 222. Disposed above the uppermost ue is a pair of upwardly curved baffles 238 and 239 which cause a thorough intermingling of the various currents of air as they emerge from between the various flues.

From Figure 6 it will be observed that the lateral pitch or inclination of the flues aids the uniform upward and zig-zag or side-to-side movement of the air in between the various flues as the air to be heated rises through the heater. As in the previously described forms, the crosssectional area of the flues progressively decreases from the bottom of the heater to the top While the effective cross-sectional area of the air passages progressively increases so as to acccommodate the. volumetric changesofp the combustion gases and air as' mentioned above.

Dampers 242, 243 and 'i244 .are .provi-dedl for controlling thefproportionate amount. of air that passes through the separate and independent air passages described aboveand shown-in Fig, 6. Thus, if. the heater is to be operated at relatively low capacity, it may bedesirable to close off oneA or two of the three separate independent. air passages. This provides aniincreased efficiency at intermediate or low demands. Y,

Any of the above describedheaters maybe provided withk humidifers, and in order to illustrate this arrangement I-have 4shown in Figure 6 a humidifier 251) inu the form of a shallow opentoppedlcontainer for water Acarried directly above the burner chamber 20|. Any suitable means, either manual or automatic, may be provided for keeping the Icontainer 250 lledwith water during the operationofthe heater.

The heaters described .above are all adapted for use with air as a heat transfer medium, but it will be apparent that other heat transfer mediums may be used, andvif. air is the preferred heat transfer medium, thepresent heater may be used with advantage inboth gravity operated and forced circulation systems. The forms of the invention shown in Figures k and 6 have certain advantages when used in a gravity system, in that-the movement of the combustion gases and air to be heated is controlled in ay positive manner. l

If it is desired to employ a heater embodying the present invention for yuse in a hotV water orA steam heating system, one or more downcirculation chambersmay be provided so as to lead the water or other medium from the4 upper part of the casing to the lowerportion thereof. Referring now more particularly to Figure 8, the heater 25H3 is particularly designed for hot water or steam systems and includes a casing 26| having anyof the flue constructions described above but adapted to contain water, disposed about the ues so as to receive heat from the combustion gases passing therethrough. One or more pairs of tubes 264 and 265 are connected with their upper ends communicating with the upper portion of the casing and with their lower ends communicating with the lower portion of the casing, thus providing for the desired circulation of the heat transfer medium in the heater. In this form of heater, the casing has a return inlet 26B at the lower portion thereof, and one or more outlet connections 261.

It will be readily apparent to anyone skilled in the art that this invention adapts itself to the combination of several sections, such as shown, assembled side by side to provide greater capacity; it also readily permits attachment of air washing, filtering, and humidifying devices to form an air-conditioning unit.

While I have shown and described above the preferred means in which the principles of the present invention have been embodied, it will be understood that my invention is not to be limited to the specific details shown and described, but that, in fact, widely different means may be employed in practicing the broader aspects of my invention.

What I claim, therefore, and desire to secure by Letters Patent is:

1. A heater comprising a casing, a combustion chamber at the lower end thereof and extending longitudinally from one end to the other, a plurality of banks of flues disposed above said combustionlchamber, with the ues of the lower bank communicating'with the .combustion chamber, said flues vbeingdisposed generally horizontally and the banks Yof .flues beingjalternately offset in Vstaggered relation from one side to the other oi ,the casing, butwith fthe ilues disposed in spaced, apart relation toprovideijor iluid movement thereover, means at ,they ends of the flues forconnecting each nue of each Ybank with the corresponding vflue of ,the bankl disposedgimmediately above so as to forma plurality of separate and independent passagesfor the hot gases.

from the combustion chamber, an outlet cham,- ber to which theoutlet ends of theaues of the last bank communicataa iuid inlet atthe lower end of the casing, and a fluidoutletat vthe upper end of the casing to accommodateagflowof fluid to be heated` by ,thel gases vpassing 4throughad flues, said heated iiuidjpassingy upwardly between theA staggered nues -in a pluralityloffpaths. Y

2. A heater -comprising acasinghaving a combustion chamber disposed,longitudinallyvin the lower portiony thereof, a plurality of Nbanks of generally horizontally disposed flues, the iluesvof each bank comprising shallow elongated conduits disposed above one another horizontally'of the casing and the banks of ues being alternately offset in, staggered relation laterally, and `each ilue having roundedeornersto facilitate fluid movement laterallynof` the `casing andupwardly between the flues along tortuous paths, anV outlet chamber at the upper endof the-,casing for the flue gases, means connecting eachgue ofV each bank with one of the flues ofthe bank next above and the lues of the uppermost bank communicating with said outlet chamber, said nues and connecting means forming a4 plurality of individualseparate Apathsfor Vthe-gases of combustion in passing from the combustion chamber to the outlet chamber, `,an.in1et in the lower portion of fsaidbasingmjand admitting air into the spaces surrounding said nues, andan outlet at the upper end of the casing to accommodate the outward movement of air from the upper end of the casing.

3. A heater comprising a casing, 4a combustion chamber at the lower portion thereof, ya :plurality of banks of generally longitudinally arranged shallow flues, each flue having a width less than the width ,of the casing and the banks of flues being arranged in alternately offset staggered relation, the ues of one bank being inclined in one direction and the flues of the next higher bank being inclined in the other direction so as to direct rising currents of heated fluid through fthe spaces between said flues laterally from one side to the vother of .the casing, conduit means connecting the ends of the flues, generally vertically ydisposed lclosure plates extending longitudinally of the flues and connecting one edge of each of the intermediate iiues of each bank with the edge of the ilue of the next higher bank that is in vertical alignment therewith, thereby deiining separate channels accommodating the vertical and lateral movement of the rising heated uid, a fluid inlet .at `the lower portion of said casing, and a fluid outlet at the upper porti-on thereof. l

4. A heater comprising a casing, a combustion chamber lat the lower portion thereof, a plurality of banks lof generally longitudinally arranged shallow flu-es, each viiue having a width less than the width of the rcasing and the banks of ues being arranged in lalternately `offset staggered relation, the flues of one .bank being inclined in one direction .and the iues of the next higher -bank being inclined in .the other Idirec-tion, so as to direct rising currents 4ofheated fluid .through thespaces between sai'd flues laterally from one side to the other of the casing, conduit means connecting the ends of the iiues, generally vertically disposed closure plates extending longitudinally of the ilues and vconnecting one edge of each ofthe intermedi-ate flues of each bank with the edgeof the flue of the next, higher bank that is in vertical alignment therewith, thereby dening separate channels accommodating the vertical and lateral movement of the rising heated iiuid, a fluid inlet at the lower portion of said casing, y.a fluid outlet at the upper portion thereof, and individual dampers for each of said separate iiuid channels.

5. In la heater, a casing, a combustion chamber at the lower portion of said casing, -a rplurality of banks of -spaced apart ues within said casing above said combustion chamber with the lower bank of flues opening into said chamber, said banksof ues being `disposed generally horizontally and alternately offset in staggered relation, the flues of each bank being disposed in stepped relation with each except the l-owermost exten-ding inward of `.said casing beyond the inner side of the next adjacent lower flue, the correspending flues of said banks being connected in series providing a plurality of separate tortuous passages for the -produots of combustion, and an outlet chamber for products o-f combusti-cn communicating withthe outlet ends of the top bank of lues.

6. In a heater, a casing having -a combustion chamber .at its lower portion and an `ouftlet for products of combustion, and a plurality of iiues within said Ycasing extending from said chamber to said outlet providing separat-e passages for products of combustion, said iiues being Iof tortuous shape providing a plurality of generally horizontal superpose'd ue banks, said banks of flues being alternately offset vinstaggered rela-` tion, the flues of each bank being disposed in stepped relation with each except the lowermost extending inward of said casing beyond the `inner side of the next adjacent lower flue.

'7. In a heater, a casing having a combustion chamber at its lower portion and an outlet for products of combustion, and a plurality Aof flues within said casing extending from said chamber to said outlet providing separate passages for products of combustion, said flues decreasing in cross-section from their inlet to their loutlet ends and being of tortuous shape providing a plurality of generally horizontal -superposed ue banks, said banks of nues being alternately oiiset in staggered relation, the ues of each bank being disposed in stepped relation witheach iiue except the lowerm-ost exten-ding inward of said casing beyond ithe inner side of the next adjacent lower flue, the ues of each -bank also being spaced apart vertically, the staggered arrangement of the bank-s of flues in conjunction with Athe stepped arrangement of the flues of the respective banks and the upwardly decreasing crosssection of the flues providing, with said casing, a passage of continuously upwardly increasing cross-sectional area for upward flow of fluid over and about said ues to be heated therefrom.

8. In a heater, a casing having a combustion chamber at its lower -portion and an ourtlet for' products of combustion, and a plurality of flues wi-thin said casing extending from said chamber to said outlet providing passages Ifor products of combustion, said flues decreasing in cross-section from their inlet `to ftheir outlet ends 4and lbeing of tortuous Ashape providing a plurality of generally horizontal superposed flue banks, the latter defining with said casing a, passage of continuously upwardly increasing cross-'sectional area for upward flow of uid over and about s-ai'd ues to be heated therefrom.

EMIL AW. RITTER. 

